Problem: $ { \left[\begin{array}{r}{-1} \\ {0} \\ {-2}\end{array}\right]+\left[\begin{array}{r}{0} \\ {1} \\ {-1}\end{array}\right] = {?} } $
To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{r}{-1}+{0} \\ {0}+{1} \\ {-2}+{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{r}{-1} \\ {1} \\ {-3}\end{array}\right]}$